When Superstorm Sandy pummeled the East Coast at the end of October, its breadth and destructiveness were enough to drag down new-car sales for the month. But already in November, carmakers were seeing Sandy’s opposite effect: a surge in new vehicle sales as buyers pocket their insurance checks and headed out to dealerships to replace their storm-ruined cars. (It’s estimated that as many as 250,000 cars were destroyed.) That tailwind added to the trend of increasing volume driven by an aging national fleet, low interest rates, and improved credit availability. Overall, sales jumped 15% compared to last year, and the annualized clip topped 15 million units, the fastest pace so far in 2012.